ACE2 expression is significantly downregulated after SARS-COV infection, contributing to hyper-activated RAS cascades.28 As a consequence, loss of ACE2 in mice confers resistance to SARS-COV infection, but also results in exacerbated vascular permeability, lung edema, neutrophil accumulation, and pulmonary dysfunction.10,29 Recombinant ACE2 protein protects against acute lung injury in mouse models of acute respiratory distress syndrome and SARS. Here, ACE2 is linked to severe acute respiratory syndrome.